The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An aircraft is driven by several turbojet engines each accommodated in a nacelle used for channeling the air flows generated by the turbojet engine, which also harbors a set of devices ensuring various functions when the turbojet engine is operating or at a standstill.
These devices may notably comprise thrust reversal means.
A nacelle generally has a tubular structure, comprising an air intake upstream from the turbojet engine, a middle section intended to surround a fan of the turbojet engine, a downstream section harboring thrust reversal means and intended to surround the combustion chamber of the turbojet engine and generally ends with an ejection nozzle, the outlet of which is located downstream from the turbojet engine.
Modern nacelles are intended to harbor a dual flux turbojet engine capable of generating via blades of the fan an air flow, a portion of which, called a hot or primary flow, circulates in the combustion chamber of the turbojet engine, and the other portion of which, called a cold or secondary flow, circulates outside the turbojet engine through a ring-shaped passage also called a vein, formed between a fairing of the turbojet engine and an internal wall of the nacelle. Both air flows are ejected from the turbojet engine through the rear of the nacelle.
The role of a thrust reverser is, during the landing of an airplane, of improving the braking capability of the latter by redirecting forwards at least one portion of the air of the secondary flow. In this phase, the reverser obstructs the vein of the cold flow and directs the latter towards the front of the nacelle, thereby generating a counter thrust which will be added to the braking of the wheels of the airplane.
The means applied for achieving this reorientation of the cold flow vary according to the type of reverser. However, the structure of a reverser comprises mobile cowls which may be displaced between a closed position or in a “direct jet” in which they close this passage and an open position or “reverse jet” in which they open in the nacelle a passage intended for the deflected flow. These cowls may fulfill a deflection function or simply an activation of other deflection means.
In the case of a thrust reverser with grids, the reorientation of the air flow is carried out by deflection grids, the cowl only having a simple sliding function aiming at exposing or covering these grids.
The translation of the mobile cowl is carried out along a longitudinal axis substantially parallel to the axis of the nacelle. Thrust reversal flaps actuated by the sliding of the cowl, allow obstruction of the cold flow vein downstream from the deflection grids, so as to optimize the reorientation of the cold flow towards the outside of the nacelle.
From the prior art, and notably from document FR 2 916 426, a thrust reverser with grids is known, the mobile cowl of which is a one-piece cowl and slidably mounted on sliders positioned on either side of the suspension pylon of the assembly formed by the turbojet engine and its nacelle.
The term “one-piece cowl” is meant a cowl with a quasi-annular shape, extending from one side to the other of the pylon without any interruption.
Such a cowl is often designated by the terms of “O-duct” with reference to the shape of a ferrule of such a cowl, as opposed to the “D duct”, which in fact comprises two half-cowls each extending over a half circumference of the nacelle.
The sliding of a cowl of the “O-duct” type between its direct jet and reverse jet positions is conventionally ensured by a plurality of actuators, of the mechano electric type (i.e., a worm screw actuated by an electric motor and displacing a nut) or of the hydraulic type (i.e., actuators actuated by pressurized oil).
In order to avoid untimely sliding of such a cowl of the “O-duct” type, which may have disastrous consequences, notably in a flight phase, several redundant locking systems are provided.
Conventionally, two systems for locking the actual actuators and a locking system, a so-called tertiary system, allowing direct locking of the sliding cowl to the supporting beam of the nacelle, currently called a “12 o'clock beam” because of its upper position relative to the circle defined by the section of the nacelle or of the jet engine pylon, are provided.
Such a tertiary locking system typically comprises two tertiary locks, positioned on either side of the 12 o'clock beam or of the jet engine pylon, each tertiary lock comprising means for locking the sliding cowl, means for blocking these locking means and means for detecting the position of said locking means. Such a lock position on one side of the 12 o'clock beam or of the jet engine pylon is generally insufficient for ensuring retention of the mobile cowl because of its flexibility.
By detecting the position of the locking means, it is possible to check that the upper edge of the sliding cowl corresponding to the relevant tertiary block is properly closed (upstream sliding position, also called “direct jet” position).
Thus, each tertiary lock fulfills a function of locking the sliding cowl on the one hand, and a function for detecting the proper closing of the corresponding edge of this cowl on the other hand.